Know the feeling Chris!
It never see`s to amaze me how the miles clock up just potering around seeking shopping , doing errands, returning home to find you have forgotten a purchase and doing the trip you have just completed all over again
That is one way of giving yourself quite a work out.
I recall one day in the summer when i had stopped at a pub for a refreshment and sat outside on a bench to enjoy it .
I duly set off again when what was about 10 miles down the road I realised I had left my sun glasses lying on the bench .
I immediatley spun around and returned , hopeing they would still be there , don`t think i ever cycled so fast in my life, as they were expensive glasses.
So that was an example to giving myself an extra 20 mile journey.
Yes! the glasses were where I had left them (phew)
Willi`c